Substrate holding technique

ABSTRACT

Disclosed is technology for holding a substrate and, specifically, an object holding apparatus including a chuck for holding an object, a holding unit for holding the chuck, a generating unit provided in the holding unit, for generating a field related to an attraction force, a member provided in the chuck and attracted by the generating unit in accordance with the field, and a supporting unit for supporting one of the generating unit and the member, for movement at least in a direction nearing the other and in a direction away from the other.

FIELD OF THE INVENTION AND RELATED ART

This invention relates generally to technology for holding a thinplate-like substrate such as a reticle or a silicon wafer, for example,in a semiconductor manufacturing procedure or any other precisionmicroprocessing procedures, for example.

As a projection exposure apparatus for projecting and transferring areticle pattern onto a silicon wafer, there is an EUV (extremeultraviolet) exposure apparatus that uses, as a light source, exposurelight of a wavelength of about 13-14 nm (extreme ultraviolet light) andthat is arranged to project and photoprint a reticle pattern onto asilicon wafer in a vacuum environment and through a mirror opticalsystem.

Referring to FIG. 8, such EUV exposure light source will be explained indetail. Denoted in the drawing at 101 is a mirror reduction opticalsystem (projection optics), and a plurality of reflection mirrors aredisposed and supported precisely inside this projection optical system101.

The projection optical system 101 is supported by a projection opticalsystem base table 106, and this base table 106 is supported by means ofa supporting mechanism 108. The supporting mechanism 108 comprises ananti-vibration table that supports the weight thereof while suppressingexternal vibration applied to the projection optical system base table106, and a metal bellows (not shown). It is so arranged that, when theload of a structure inside a vacuum chamber 107 (i.e., projectionoptical system 101 and base table 106) is supported from outside thechamber 107, the vacuum level inside the vacuum chamber can bemaintained while, on the other hand, any positional deviation betweenthe vacuum chamber and the thus supported structure can be resilientlyabsorbed.

There is a mask 103 above the projection optical system 101, and thewhole of the bottom face of the mask 103 is held by means of a maskchuck 115. The mask chuck 115 is mounted to a mask stage 102 above it.The mask 102 stage can be driven by means of an actuator (not shown) forrepeated scan exposure of the mask 103 pattern. Denoted in the drawingat 104 is a portion of mask stage measurement light, taking theprojection optical system base table 106 as the reference ofmeasurement. In the exposure apparatus of FIG. 8, the position of themask stage 102 is measured with respect to multiple axes, by means ofinterferometers using laser light, and the mask stage 102 is positionedon the basis of it. Disposed above the mask stage 102 is a mask stageguide 113 that guides the mask stage 102 for multiple-axis motions. Themask stage guide 113 is supported by a mask stage damper base table 114.

Disposed below the projection optical system 101 is a wafer stage 109being movable while holding a wafer (substrate to be exposed) 105.Denoted at 110 is a portion of wafer stage measurement light, taking theprojection optical system base table 106 as the reference ofmeasurement, like for the mask stage 102. The position of the waferstage 109 is measured with respect to multiple axes, by means ofinterferometers using laser light, and the wafer stage 109 is positionedon the basis of it.

Disposed below the wafer stage 109 is a wafer stage guide 111 thatguides the wafer stage 109 for multiple-axis motions. As regards theguiding method, a static pressure arranged for use in a vacuum may beused, for example. The wafer stage guide 111 is supported by a waferstage damper base table 112 which is arranged to support the flatness ofthe guiding surface of the wafer stage guide 111 very precisely. Thewafer stage damper base table 112 is supported by an anti-vibrationtable or the floor on which the apparatus is mounted.

In exposure operation, EUV light projected from an illumination system(not shown) is reflected by the exposure pattern surface of the mask 103and then is reflected along an optical path (not shown) inside theprojection optical system 101, whereby it is projected upon the siliconwafer 105. While the wafer 105 is held by the wafer stage 109, the waferstage 109 and the mask stage 102 having a mask 3 mounted thereon aremeasured with respect to multiple axes by using laser light and thenthey are positioned. Then, the wafer 105 and the mask 103 are scanninglymoved in synchronism with each other or, alternatively, one of them isheld stationary and sequential exposure is carried out. As regards theposition of the mask stage 102, as an example, the position in avertical direction (Z direction) of the mask reflection surface, theposition with respect to two orthogonal directions (X and Y directions)along a plane (X-Y plane) perpendicular to that vertical direction, androtations about the three orthogonal axes (X, Y and Z axes) may bemeasured.

FIG. 9 is an enlarged view of the mask chuck 115 and the mask stage 102described above. There is a possibility that a foreign particle such asat 116 is sandwiched between the chucking surface of the mask chuck 115and the mask 103, and it adversely influences the flatness of the mask103. In consideration of it, the mask chuck 115 is demountably mountedto the mask stage 102, and the cleaning operation for the mask chuck 115is carried out outside the vacuum chamber 107.

As a fixing device for attracting and holding a thin plate-like memberin a vacuum environment, Japanese Patent No. 3076727 discloses atechnique according to which electrostatic attracting means arranged toattract and hold, upon a stage and through an electrostatic force, anelectrically conductive cassette for holding a sample such as a glassmask or a wafer, provided for electron beam irradiation, is mounted tothe stage. Also, as an exposure apparatus in which a wafer is heldfixed, Japanese Laid-Open Patent Application, Publication No.2003-142393 discloses a technique according to which a pallet has awafer electrostatic chuck for fixing a wafer. Further, as an exposureapparatus having a mask holding member for mountably and demountablyholding an exposure mask, Japanese Laid-Open Patent Application,Publication No. 11-288099 discloses a technique according to which anexposure mask is positioned by manually pressing it against apositioning pin of a mask holding member and, in this state, the mask isheld by a toggle clamp.

In a mechanism for demounting and clearing a mask chuck, chucking(attracting and holding) the mask chuck from the stage causesdegradation of the mask chuck flatness. Also, a positional deviation ofthe mask chuck with respect to the mask stage leads to degradation ofthe mask holding precision. Moreover, an electricity supplying systemfor mounting and demounting a mask to and from the mask chuck has acomplicated structure.

SUMMARY OF THE INVENTION

It is accordingly an object of the present invention to provide asubstrate holding technique by which a substrate can be held at highsurface precision, in a vacuum environment.

In accordance with an aspect of the present invention, there is providedan object holding apparatus, comprising: a chuck for holding an object;a holding unit for holding said chuck; a generating unit provided insaid holding unit, for generating a field related to an attractionforce; a member provided in said chuck and attracted by said generatingunit in accordance with the field; and a supporting unit for supportingone of said generating unit and said member, for movement at least in adirection nearing the other and in a direction away from the other.

In accordance with another aspect of the present invention, there isprovided an object holding apparatus, comprising: a chuck for holding anobject; a holding unit for holding said chuck; and a measuring unit formeasuring relative displacement between said chuck and said holdingunit.

In accordance with a further aspect of the present invention, there isprovided an object holding apparatus, comprising: a chuck for holding anobject; and a holding unit for holding said chuck, wherein said chuckincludes a first electrode for attracting the object with anelectrostatic force and a second electrode for attracting said holdingunit with an electrostatic force.

Thus, the present invention can provide unique and useful substrateholding technology for holding a substrate at high surface precision.

These and other objects, features and advantages of the presentinvention will become more apparent upon a consideration of thefollowing description of the preferred embodiments of the presentinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of attracting means in a first embodiment ofthe present invention.

FIG. 2 is a fragmentary and enlarged view of the attracting means ofFIG. 1.

FIG. 3 is a schematic view of attracting means in a second embodiment ofthe present invention.

FIG. 4 is a schematic view of attracting means in a third embodiment ofthe present invention.

FIG. 5 is a schematic view of a fourth embodiment of the presentinvention, wherein a mask stage having attracting means is provided witha sensor.

FIG. 6 is a flow chart for explaining the sequence of devicemanufacture.

FIG. 7 is a flow chart for explaining a wafer process in the procedureof FIG. 6, in detail.

FIG. 8 is a schematic view of exposure apparatus.

FIG. 9 is an enlarged view a mask stage and a mask chuck having a maskmounted thereon.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will now be describedwith reference to the attached drawings.

Embodiment 1

A first embodiment of the present invention will be described withreference to FIGS. 1 and 2. FIGS. 1 and 2 illustrate, in enlargedmagnification, a mask stage and a mask chuck portion, disposed above aprojection optical system of an exposure apparatus such as shown in FIG.8. In FIG. 1, denoted at 1 is a mask chuck (substrate holding member),and denoted at 2 is a mask stage (stage) movable in a predetermineddirection. The mask chuck has targets formed thereon, for measurement ofposition, angle and focus of the mask stage 2. The scan direction of themask stage 2 is in Y-axis direction in FIG. 1. The mask chuck 1 having amask (substrate) 3 held thereon is mounted to the mask stage 2. The maskchuck 1 and the mask stage 2 are provided with attracting means formountably and demountably supporting the mask chuck 1 on the mask stage2. The attracting means comprises a coil ion core 7 (second member)provided at the mask stage 2 side and a ferromagnetic material member(first member) provided at the mask chuck 1 side. In FIG. 1, actuallythere are two sets of attracting means disposed along X direction.

Each coil iron core 7 has an exciting coil 4 wound around the core, andthe coil 7 is supported on the mask stage 2 with freedoms in Zdirection, around Y axis (small freedom) and around X axis in FIG. 1, bymeans of a leaf spring (resilient material) 6. In this example, therigidity of the leaf spring 6 is lower than that of the mask chuck 1.Namely, the leaf spring 6 has a low rigidity only with respect to avertical direction of the mask reflection surface. The ferromagneticmaterial member 5 is a plate-like member made of metal, and it isembedded at such position where the coil ion core 7 can contact theretoagainst the force of the leaf spring 6, in the manner that the member 5surface becomes approximately coplanar with the upper surface of themask chuck 1.

The mounting structure for the coil ion core 7 will be described ingreater detail, with reference to FIG. 2. At a nominal position of theleaf spring 6, the coil iron core 7 is placed inwardly, inside the maskstage 2, of the contact surface between the mask stage 2 and the maskchuck 1, that is, the surface of the ferromagnetic material member 5.With this arrangement, the free end face of each leg of the coil ironcore 7 can be opposed to the ferromagnetic material member 5 with aclearance. For attraction of the coil iron core 7 and the ferromagneticmaterial member 5, while the leaf spring 6 deforms, the coil iron core 7is attracted toward the ferromagnetic material 5 side and is broughtinto contact with it, whereby the mask chuck 1 is held. In this case,since the leaf spring 6 can absorb displacement, there is no possibilitythat, due to the surface precision matching between the contact surfacesof the coil iron core 7 and the ferromagnetic material member 5, a forceis applied to the mask chuck 1 to cause deformation thereof.

In the attracting means of the first embodiment, the leaf spring 7 ismounted on the coil iron core 7 side to support the same. However, theinvention is not limited to this. The leaf spring 6 may be mounted onthe ferromagnetic material member 5 side to support the same. It is tobe noted here that, regarding the attracting means, there are two setsof attracting means also with respect to the Y-axis direction.

At a lower portion inside the mask chuck 1, opposed to the mask 3, thereare tow sets of plate-like electrostatic chuck electrodes 8 for holdingthe mask 3. Each electrostatic chuck electrode 8 is connected to theferromagnetic material member 5 through a wire or a metal plate, whileon the other hand the coil iron core 7 contacted to the ferromagneticmaterial member 5 is connected to an electricity supplying unit (notshown) through a wire or the like. In this example, the contact surfacebetween the coil iron core 7 and the ferromagnetic material member 5,producing an electromagnetic force, is defined or functions as a portionof an electricity supplying path for the electrostatic chuck electrode 8of the mask chuck 1. In this embodiment, as described above, the contactsurface between the coil iron core 7 and the ferromagnetic materialmember 5 is included in the electricity supplying path for theelectrostatic chuck electrode 8. However, the invention is not limitedto this. Along a different path, electricity can be supplied to theelectrostatic chuck electrode 8. Furthermore, in this embodiment, thecontact surface that produces an electromagnetic force functions as aheat transfer path for cooling the mask chuck 1 and the mask 3. In thiscase, any produced heat can flow from the contact surface to the coiliron core and the wire, for example, and is heat-exchanged. If thecontact surface between the coil iron core 7 and the ferromagneticmaterial member 5 is not used as the electricity supplying path, as theferromagnetic material member 5 a material having low electricconductivity, such as ferrite, may be used.

In the first embodiment, for holding of the mask chuck 1 by the maskstage 2, the exciting coil 4 is energized and, in response, a magneticfield is produced from the coil iron core 7 by which the ferromagneticmaterial member 5 embedded in the mask chuck 1 is magnetized and wherebythe mask chuck 1 is attracted. After the attraction and even after thevoltage supply to the exciting coil 4 is discontinued, since theferromagnetic material member 5 has already been magnetized, the coiliron core 7 and the ferromagnetic material member 5 are mutuallyattracted to each other, such that the mask chuck 1 can be continuouslyheld on the mask stage 2. For demounting the mask chuck 1 from the maskstage 2, an electric current is applied in an opposite direction to theexciting coil 4 and thus an opposing magnetic field is applied to theferromagnetic material member 5, whereby it is demagnetized. Further,when the coil iron core 7 and the ferromagnetic material member 7 areattracted to each other, owing to the electricity supplying pathextending through the contact surface therebetween producing anelectromagnetic force, an electric potential is applied to the two,left-hand side and right-hand side electrostatic chuck electrodes 8. Bymeans of electric charges in that occasion, the mask chuck 1 canelectrostatically attract approximately the entire surface of the maskbottom face and hold the same tightly.

Embodiment 2

A second embodiment of the present invention will be described withreference to FIG. 3. In FIG. 3, like reference numerals are assigned tocomponents corresponding to those of the FIG. 1 embodiment, anddescription therefor will be omitted. Only distinctive features will beexplained.

In the second embodiment, the second member at the mask stage 2 side(i.e., coil iron core 7) and the first member at the mask chuck 1 side(i.e., ferromagnetic material member 5) are disposed close to each otherwith a clearance, like the structure shown in FIG. 2. By disposing thecoil iron core 7 and the ferromagnetic material member 5 opposed to eachother with a clearance as described above, unwanted deformation of themask chuck 1 due to their mutual surface precision can be avoided.Furthermore, each coil iron core 7 is provided with a piezoelectricactuator 10 or, alternatively, a distance adjusting mechanism (notshown), such that the flatness of the mask chuck 1 can be correctedthereby.

For the flatness correction, the gap distance (clearance) between thecoil iron core 7 and the ferromagnetic material member 5 may be adjustedby means of the piezoelectric actuator 10 or the like, while theflatness is measured by using an external interferometer or any othermeasuring device. As an alternative, distortion sensors 11 may beembedded in the mask chuck 1, at plural locations, and the adjustmentmay be done while measuring the surface shape by use of these distortionsensors 11. As for such adjustment, measurement and adjustment may bedone at start of the exposure apparatus, for example, or it may be madein various ways. It should be noted that, to each electrostatic chuckelectrode 8, an electricity supplying path such as wire or metal plate,for example, is connected, and this electricity supplying path is inturn connected to an electricity supplying unit, not shown. In thiscase, the contact between the mask chuck 1 and the mask stage 2 in theelectricity supplying path is accomplished by means of a brush member,for example, which is provided on at least one of or each of the maskchuck 1 side and the mask stage 2 side. The attraction of the mask 3 issimilar to that of the first embodiment. In this case, by means of theelectrostatic chuck electrodes 8, approximately the whole surface of themask 3 bottom face can be held tightly.

Embodiment 3

A third embodiment of the present invention will be described withreference to FIG. 4. In FIG. 4, like reference numerals are assigned tocomponents corresponding to those of the embodiments of FIGS. 1-3, anddescription therefor will be omitted. Only distinctive features will beexplained.

In the third embodiment, in order that a mask chuck 1 is held on a maskstage 3 by electrostatic attraction force, mask-chuck electrostaticchuck electrodes (electrostatic attracting means) 9 are provided abovethe mask chuck 1. Each electrostatic chuck electrode 8 is connected toan electricity supplying unit (not shown) through an electricitysupplying path such as wire or metal plate, for example. In thisexample, a connecting member such as a brush, for example, is used atthe connection of electricity supplying path, between the mask chuck 1and the mask stage 2. With this structure, when the mask chuck 1 ismounted to the mask stage 2, from an electricity supplying unit (notshown), an electric potential is applied to the mask-chuck electrostaticchuck electrodes 9 and, in response to it, the mask chuck 1 itself isattracted to the mask stage 2 by electrostatic attraction force, and itis held thereby. Since high-precision flat plane is obtainable with anelectrostatic chuck (attraction by electrostatic), application ofunwanted deformation to the mask chuck 1 can be avoided assuredly. As analternative, the electrostatic chuck electrodes 9 may be provided on themask stage 2 side to attract and hold the mask chuck 1. The attractionof the mask 3 is similar to that of the first embodiment. Also in thiscase, approximately the entire surface of the mask 3 bottom face can beattracted and held tightly, by means of the electrostatic chuckelectrodes 8.

Embodiment 4

A fourth embodiment of the present invention will be described withreference to FIG. 5. In FIG. 5, like reference numerals are assigned tocomponents corresponding to those of the embodiments of FIGS. 1-4, anddescription therefor will be omitted. Only distinctive features will beexplained.

In the fourth embodiment, at the bottom surface portion of the maskstage 2, avoiding the mask chuck 1, a chuck position measuring device(interferometer) 12 which is a displacement measuring sensor fordetecting any positional deviation between the mask stage 2 and the maskchuck 1, is provided. In case there occurs a positional deviationbetween the mask stage 2 and the mask chuck 1, the exposure sequence isstopped and alignment of the mask 3 is carried out again.

In the forth embodiment, the chuck position measuring device 12 isprovided on the mask stage 2 of the first embodiment (FIG. 1). However,the invention is not limited to this. It may be mounted to the maskstage 2 of the second embodiment or of the third embodiment. Further, inplace of the mechanism for measuring a relative displacement, from themask stage 2 side, a mask stage measurement reference may be used anddisplacement of the mask chuck 1 may be measured directly.

Where a stage system such as described above is used as a mask stage ofa projection exposure apparatus such as shown in FIG. 8, when the maskchuck is chucked, deformation of the mask chuck resulting from thesurface shape of the contact area, including a foreign particle, if any,can be prevented effectively and, in turn, the surface precision of themask as well as the performance of the apparatus can be improvedsignificantly.

Although in the foregoing description the invention has been describedwith reference to embodiments wherein it is applied to a mask stagesystem, the present invention is applicable also to a wafer stagesystem, as a matter of course.

Embodiment 5

Next, an embodiment of a device manufacturing method which uses anexposure apparatus such as described above, will be explained.

FIG. 6 is a flow chart for explaining the procedure of manufacturingvarious microdevices such as semiconductor chips (e.g., ICs or LSIs),liquid crystal panels, CCDs, thin film magnetic heads or micro-machines,for example. Step 1 is a design process for designing a circuit of asemiconductor device. Step 2 is a process for making a mask on the basisof the circuit pattern design. Step 3 is a process for preparing a waferby using a material such as silicon. Step 4 is a wafer process which iscalled a pre-process wherein, by using the thus prepared mask and wafer,a circuit is formed on the wafer in practice, in accordance withlithography. Step 5 subsequent to this is an assembling step which iscalled a post-process wherein the wafer having been processed at step 4is formed into semiconductor chips. This step includes an assembling(dicing and bonding) process and a packaging (chip sealing) process.Step 6 is an inspection step wherein an operation check, a durabilitycheck an so on, for the semiconductor devices produced by step 5, arecarried out. With these processes, semiconductor devices are produced,and they are shipped (step 7).

FIG. 7 is a flow chart for explaining details of the wafer process. Step11 is an oxidation process for oxidizing the surface of a wafer. Step 12is a CVD process for forming an insulating film on the wafer surface.Step 13 is an electrode forming process for forming electrodes upon thewafer by vapor deposition. Step 14 is an ion implanting process forimplanting ions to the wafer. Step 15 is a resist process for applying aresist (photosensitive material) to the wafer. Step 16 is an exposureprocess for printing, by exposure, the circuit pattern of the mask onthe wafer through the exposure apparatus described above. Step 17 is adeveloping process for developing the exposed wafer. Step 18 is anetching process for removing portions other than the developed resistimage. Step 19 is a resist separation process for separating the resistmaterial remaining on the wafer after being subjected to the etchingprocess. By repeating these processes, circuit patterns are superposedlyformed on the wafer.

With these processes, high density microdevices can be manufactured.

Although some preferred embodiments of the present invention have beendescribed in the foregoing, in different aspects, the present inventioncan be embodied as follows.

(1) In an exposure apparatus wherein a pattern formed on an original isprojected, in a vacuum environment, onto an exposure substrate to beexposed, through a projection optical system, wherein, while moving bothof the original and the exposure substrate or only the exposuresubstrate relative to the projection optical system by use of a stagesystem, the pattern of the original is repeatedly photoprinted on theexposure substrate, characterized by an original mounting and holdingmember for mounting the original to the stage system, wherein at leastone of attracting and holding means provided at the original mountingand holding member side and attracting and holding means provided at thestage system side is mounted through a resilient member having arigidity lower than that of the original mounting and holding member.

(2) In an exposure apparatus according to Item (1) above, the resilientmember is a resiliency member having a low rigidity only in a verticaldirection to the mask reflection surface.

(3) In an exposure apparatus according to Item (1) or (2) above,attracting and holding means having a clearance is provided between theoriginal attracting and holding member and the attracting and holdingmeans at the stage system side, wherein the flatness of the originalmounting and holding member is measured and the clearance distances atplural locations of the attracting and holding means are adjusted.

(4) In an exposure apparatus according to Item (3) above, measuringmeans for measuring the surface precision of the original mounting andholding member uses a distortion sensor.

(5) In an exposure apparatus according to Item (4) above, the clearancedistance between a ferromagnetic material member and a coil iron core iscontrolled by means of an actuator and on the basis of an output valueof the distortion sensor or on the basis of pre-measured value.

(6) In an exposure apparatus according to any one of Items (1) to (5),the attracting mechanism of the attracting and holding means uses anelectromagnetic force or an electrostatic attraction force.

(7) In an exposure apparatus according to any one of Items (1)-(6), adisplacement measuring sensor is provided between the original mountingand holding member and the stage system.

(8) In an exposure apparatus according to any one of Items (1)-(7), theoriginal mounting and holding member is provided with a target formeasurement of position, angle, or focus of the stage system.

(9) In an exposure apparatus according to any one of Items (1)-(8), thecontact surface for generating an electromagnetic force functions as anelectricity supplying path to the original mounting and holding member.

(10) In an exposure apparatus according to any one of Items (1)-(9), thecontact surface for generating an electromagnetic force functions as aheat transfer path for cooling the original mounting and holding memberand the mask.

(11) A device manufacturing method characterized by manufacturing adevice by use of an exposure apparatus as recited in any one of Items(1)-(10).

While the invention has been described with reference to the structuresdisclosed herein, it is not confined to the details set forth and thisapplication is intended to cover such modifications or changes as maycome within the purposes of the improvements or the scope of thefollowing claims.

This application claims priority from Japanese Patent Application No.2003-324214 filed Sep. 17, 2003, for which is hereby incorporated byreference.

1. An object holding apparatus, comprising: a chuck for holding anobject; a holding unit for holding said chuck; a generating unitprovided in said holding unit, for generating a field related to anattraction force; a member provided in said chuck and attracted by saidgenerating unit in accordance with the field; and a supporting unit forsupporting one of said generating unit and said member, for movement atleast in a direction nearing the other and in a direction away from theother.
 2. An apparatus according to claim 1, wherein said generatingunit generates a magnetic field.
 3. An apparatus according to claim 2,wherein said generating unit includes a core and a coil for energizingthe core.
 4. An apparatus according to claim 2, wherein said memberincludes a magnetic material.
 5. An apparatus according to claim 1,wherein said supporting unit includes a member having a rigidity lowerthan that of said chuck, with respect to said directions.
 6. Anapparatus according to claim 5, wherein said supporting unit includes aleaf spring.
 7. An apparatus according to claim 1, wherein saidgenerating unit and said member are brought into contact with eachother, by the attraction force.
 8. An apparatus according to claim 7,wherein a heat abstraction path is defined by the contact.
 9. Anapparatus according to claim 7, wherein said chuck includes a mechanismfor holding the object, and wherein an electricity supplying path isdefined by the contact.
 10. An apparatus according to claim 1, whereinsaid holding unit holds said chuck by means of the attraction force andwithout contact.
 11. An apparatus according to claim 10, wherein saidsupporting unit includes an actuator for moving one of said generatingunit and said member.
 12. An apparatus according to claim 11, whereinsaid actuator comprises a piezoelectric device.
 13. An apparatusaccording to claim 7, further comprising a distortion sensor formeasuring distortion of said chuck, wherein said actuator is controlledon the basis of an output of said distortion sensor.
 14. An apparatusaccording to claim 7, further comprising a measuring unit for measuringrelative displacement of said chuck and said holding unit.
 15. Anapparatus according to claim 1, wherein said generating unit generatesan electrostatic field.
 16. An object holding apparatus, comprising: achuck for holding an object; a holding unit for holding said chuck; anda measuring unit for measuring relative displacement between said chuckand said holding unit.
 17. An object holding apparatus, comprising: achuck for holding an object; and a holding unit for holding said chuck,wherein said chuck includes a first electrode for attracting the objectwith an electrostatic force and a second electrode for attracting saidholding unit with an electrostatic force.
 18. An exposure apparatus,comprising: exposure means for exposing a substrate to a pattern of anoriginal; and an object holding apparatus as recited in any one ofclaims 1, 16 and
 17. 19. A device manufacturing method including aprocess for exposing a substrate to a pattern of an original by use ofan exposure apparatus as recited in claim 18.